Close-up multispectral images of the surface of comet 67P/Churyumov-Gerasimenko by the ROLIS camera onboard the Rosetta Philae lander

In November 2014 the Philae lander onboard Rosetta is scheduled to land on the surface of comet 67P/Churyumov-Gerasimenko. The ROLIS camera will provide the ground truth for the Rosetta OSIRIS camera. ROLIS will acquire images both during the descent and after landing. In this paper we concentrate on the post-landing images. The close-up images will enable us to characterize the morphology and texture of the surface, and the shape, albedo, and size distribution of the particles on scales as small as 0.3 mm per pixel. We may see evidence for a dust mantle, a refractory crust, and exposed ice. In addition, we hope to identify features such as pores, cracks, or vents that allow volatiles to escape the surface. We will not only image the surface during the day but also the night, when LEDs will illuminate the surface in four different colors (blue, green, red, near-IR). This will characterize the spectral properties and heterogeneity of the surface, helping us to identify its composition. Although the ROLIS spectral range and resolution are too limited to allow an exact mineralogical characterization, a study of the spectral slope and albedo will allow a broad classification of the solid surface phases. We expect to be able to distinguish between organic material, silicates and ices. By repeated imaging over the course of the mission ROLIS may detect long term changes associated with cometary activity.